Electrophysiologic Studies
Transmembrane action potentials (APs) of PVs, SVC, RA, and LA were
recorded by machine-pulled quartz glass microelectrodes filled with 3 M
KCl (resistance of 10-20 M Ω) connected to an amplification system. Two
bipolar silver stimulating electrodes were attached to each preparation
in the tissues. Recording sites were located 4 mm from stimulating
electrodes. Transmembrane APs were digitized with an analog-to-digital
converter and stored to a PC for subsequent analysis. Preparations were
stimulated at a basic cycle length (BCL) of 1000ms during the
equilibration period (0.5 h). Regular pacing was achieved by bipolar
silver electrodes attached to each preparation (1-3ms duration period
and 2.5 times diastolic threshold intensity). Isoproterenol (1uM)
combined with high calcium (5.4mM) was used to induce DADs and triggered
activity in PVs, SVC, RA and LA preparations before and after exposure
to Triarylmethane-34(TRAM-34, a selective antagonist of KCa3.1,
HY-13519, Med Chem Express, USA). TRAM-34 was dissolved in dimthyl
sulfoxide to form a solution of 5uM concentration. Isoproterenol was
dissolved in distilled water to form 1uM solution.